The reason they make a case for back to sleep is because in a baby who has low serotonin levels, sleeping on the stomach can cause an at risk baby to inhale higher levels of carbon dioxide than an infant with normal levels. The article states: "When the infant is breathing in the face-down position, he or she may not get enough oxygen. An infant with a normal brainstem would turn his or her head and wake up in response. But a baby with an intrinsic abnormality is unable to respond to the stressor." The low serotonin levels seem to be related to a chronic abnomality in the medulla, not something that comes and goes from something like CIO. I'm certainly not saying that CIO is good for babies or that it doesn't lower serotonin levels but the study is talking about babies that INTRINSICALLY have low serotonin. Even if you were the most attached parent your baby could have low serotonin levels because of a brain abnormality.
The reason this study is exciting is that it is a big step in identifying babies that are at risk (those with this brain abnormality) and making sure those babies slept on their backs free of anything that could obstruct their breathing sounds logical to me.